Airfoil



April 29, 1969 E ARNHOLDT 3,441,236

AIRFOIL Filed Jan. 16, 1967 CONTROL [/61 51 '55 Magus \5 50 m 55 31 5c15d 55 R1 7 a II 52/6 flew/mar ATTORNEYS United States Patent 3,441,236AIRFOIL Eric Arnholdt, 7108 Seacliff Road, McLean, Va. 22101 Filed Jan.16, 1967, Ser. No. 609,431 Int. Cl. 1864c 21/02, 3/00; B64d 15/02 US.Cl. 244-42 Claims ABSTRACT OF THE DISCLOSURE An apparatus for providinglift in a fluid medium having an adjustable slot-like passage extendingfrom the underneath pressure surface tothe upper suction surface forproviding additional high velocity fluid flow over the latter. A deicingsystem channeling heated air chordwise along the passage and through itsdischarge nozzle is positioned within the airfoil.

The present invention relates to improvements in airfoils and, moreparticularly, relates to improvements in airfoils having a liftmodifying passage formed therein.

In my prior US. patent application, Ser. No. 425,853, filed Jan. 15,1965, entitled, Airfoil, now US. Patent 3,298,636, issued I an. l7,1967, there is provided an improved airfoil having an upper suctionsurface formed in an undulating fashion with relatively spaced crestsand valleys for enhancing the lift-to-drag ratio. As explained in thisearlier patent this desired result is accomplished by providing apassage through the airfoil extending substantially parallel to thefluid flow from the underneath pressure surface to the upper suctionsurface. This passage terminates in a restricted nozzle to cause a highvelocity stream of fluid to be expelled tangentially of said valleythereby causing the fluid flow to follow the curvature of the valley aswell as the crest in a fashion to materially improve the lift and reducethe drag, and to thus enhance the lift-to-drag ratio.

The present invention is concerned with the provision of structure usedto control the flow of air through this type of lift modifying passageand thus a main objective is to thereby provide a means for efficientlycontrolling the velocity and mass flow of air through the passage andinto the boundary layer region of the slipstream over the lift orsuction surface. Broadly speaking, the apparatus of the presentinvention is not limited to use with the specific airfoil disclosed andclaimed in this previous patent, but can be utilized for the control ofthe fluid flow through similar passages in conventional airfoils, whichare primarily designed to prevent premature separation of the fluid flowand thus a reduction in the drag coeflicient, for example, as shown inthe US. patent to Grant, No. 2,649,265, issued Aug. 18, 1953.

It is an additional objective of the present invention to provide anairfoil with a passage of the type described having a novel deicingarrangement, which is effective to prevent the undesirable build-up ofice in the passage.

Briefly, the apparatus of the present invention includes a passage inthe airfoil which is formed of opposed inner wall members, the innerWall members being spaced to form an enlarged mouth opening at thepressure surface and a restricted nozzle opening at the suction surface.At least one of the wall members is movable, and preferably the upperwall member is formed of a series of articulated sections which arecapable of being selectively moved toward and away from the opposed orlower wall member. With this construction, the cross sectional area ofthe passage may be easily adjusted to vary the mass flow of fluidthrough the passage, and thereby vary the velocity and effectiveness ofthe lift modifying stream of fluid exiting through the nozzle andtangentially onto the "ice suction surface. Also, of importance is theprovision of an extensible join-t in said upper wall member, whichallows a maximum adjustable range of movement of said wall member. As aresult of this feature, the forwardmost articulated sections may assumein one limit position, a closing relationship across the mouth of thepassageway to cut off the flow of fluid through the passage, and at theother limit of movement, the mouth is allowed to be wide open formaximum flow through the passage, as desired. Thus, in accordance withthe present invention, the lift modifying passage may be fully openedfor maximum mass flow during periods when high lift is required, such asduring take off and landing; then the passage can be adjusted to assumean intermediate position for normal flight; and finally the passage canbe fully closed whenever the lift modifying effect is not desired.

It should be noted that the adjustable lift modifying effect of theairfoil of the invention is gained without a change in the camber of thewing or a change in the rearward sweep of the wing, as has been proposedin the past, and the airfoil of the invention is accordingly of muchsimpler design for savings in cost and weight, which factors are ofutmost importance in craft of this type. Furthermore, since the crosssection and the position of the wing remain unchanged in the airfoil ofthe present invention, it is considered to be more reliable and notsubject to the costly maintenance problems usually associated with theseprior art variable shaped or variable sweep wing constructions.

In accordance with the other but related aspect of the presentinvention, the airfoil is provided with means for preventing thebuild-up of ice in the passage, thus insuring efficient operation of theapparatus under adverse weather conditions. Preferably, the workingmedium for the deicing system is supplied by the hot air exhaust orcompressor bleed from the aircrafts engines and this air is directedfirst along the inside surfaces of the wall members forming the passageand then directed into the restricted nozzle of the passage where icingconditions are more prevalent. With this arrangement, it has been foundthat maximum ice prevention is obtainable along the entire length of thepassage with a minimum amount of adverse turbulence being introducedinto the stream of fluid passing through the passage. Furthermore, flapvalves are provided on the orifices which introduce the heated air intothe restricted nozzle to allow the proper proportioning of the heatedfluid with the high velocity stream of air for maximum acceleration ofsaid stream resulting from the mixing of the fluids.

In a modification of the deicing system of the present invention,continuous passageways are provided along the inside of the wall membersforming the passage to confine the floW of heated air adjacent said wallmember for maximum heat transfer. On the upper wall member, which, itwill be remembered, has articulated sections in the preferred embodimentillustrated, this passageway is preferably formed by a series ofarticulated parallel deflectors interconnected to said sections by linksfor adjustable movement therewith.

Still other objects and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein I have shown and described only thepreferred embodiments of the invention, simply by way of illustration ofthe best modes contemplated 'by me of carrying out my invention. As willbe realized, the invention is capable of other and differentembodiments, and its several details are capable of modification invarious obvious respects, all Without departing from the invention.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive.

In the drawings:

FIGURE 1 is a cross-sectional view of a preferred embodiment of theairfoil of the present invention having a lift modifying passage shownin the normal open mode of operation for normal lift modifying andanti-icing effects;

FIGURE 2 is a cross-sectional view of the airfoil of FIGURE 1illustrating the closed mode of operation for no-lift modifying andmaximum deicing efiects;

FIGURE 3 is a cross-sectional view of the airfoil of FIGURE 1 showingthe operating mode for maximum lift effect on the airfoil;

FIGURE 4 is a detailed cross-sectional view taken along line 44 ofFIGURE 3 showing the sealing arrangement at the edges of the wallmembers; and

FIGURE 5 illustrates a modification of the airfoil of the inventionhaving continuous heated air passageways along the upper and lower wallmembers of the passage.

Referring now specifically to FIGURE 1 of the accompanying drawing,there is illustrated an airfoil having a leading edge 11 and a trailingedge 12; it being understood that said trailing edge 12 may lead to avalley of an undulating type airfoil such as shown in my previous patentor may terminate in a conventional trailing edge, as desired. In anycase, the airfoil 10 has a conventional upper suction surface 13 and alower pressure surface 14 extending between the leading and trailingedges 11, 12.

Any number of vertical ribs 15 (only one being shown in the drawing) areprovided to afford stability to the airfoil construction, and if desiredconventional lightening holes 16 may be incorporated in the interiorareas, as illustrated. Bounded on the sides by adjacent ones of theseribs 15 is a slot-like passage 17, which extends substantially parallelto the flow of the slipstream across the airfoil 10 from a mouth 18formed in the pressure surface 14 to an egress opening 19 formed in thesuction surface 13. For ease of discussion, the passage 17 itself may bedefined as having a forward accelerating section, generally designatedby the reference numeral 20, and a restricted nozzle, generallydesignated by the reference numeral 21. As will be realized, during theoperation the fluid entering the mouth 18 is accelerated over the lentghof the forward section 20 and ejected at a high velocity through thenozzle 21 into the boundary layer region of the fluid flowing over theairfoil 10 for improving the lift on the airfoil 10.

The forward section 20 of the passage 17 is formed by an upper wallmember 25, which in the preferred embodiment shown includes any numberof articulated sections 25a-25d connected together by pivot hinges 26and a lower wall member 27 which in the embodiment illustrated is fixed.It is contemplated that other types of movable wall structures could beutilized in lieu of the wall member 25 if desired in accordance with thebroader teachings of the present invention, and that the fixed wall 27could, if required, also be made to be adjustable.

In the preferred embodiment illustrated, each of the sections 25b, 25c,25d is adjustably operated by any number of hydraulic cylinder units 30,31, 32 (only one each being shown) that are connected in any suitablemanner to the airfoil structure, as by a cross bar 33 carrier betweenthe ribs 15. As shown, the forwardmost section 25a is preferably shorterthan the remaining sections 25b25d and performs the important functionof varying the width of the mouth 18. For example, note the position ofthe section 25a in the plane of the mouth 18 in FIGURE 1, thus limitingthe cross sectional size of the same to that shown by the referenceindicia M in this figure. Also, it should be noted that the forwardmostsection 25a does not include aseparate operating cylinder and thus isoperated as a follower, i.e. movement of section 25a is gained from thecombined operation of the hydraulic cylinders 30, 31 to properlyposition the pivot hinges 26, as shown in the drawing. The hydrauliccylinders 30-32 are provided with suitable control means 34, which isinterconnected by hydraulic lines 35, 36, 37 to the respectivecylinders; said control means being capable of selectively positioningeach section 25b-25d as required. The position of the wall member 25 asshown in FIGURE 1 can be considered to be the normal flight positionwith increased lift being provided by the airfoil 10 from the flow offluid through the passage 17 as noted by the flow arrows in this figure.

As can best be seen in FIGURE 2, the rearwardmost section 25d includesan extensible joint, generally designated by the reference numeral 40,which allows the wall member 25 to expand whereby the passage 17 may beclosed at the mouth 18 by deployment of the articulated sections 25a,25b as shown. This position of the wall member 25 thus represents alimit position in the direction toward the fixed wall member 27 and isutilized when the lift modifying effects of the stream of fluid affordedby the passage 17 are not desired. At any intermediate position betweenthe positions of FIGURES 1 and 2, a reduced amount of fluid flowsthrough the passage 17 for reduced velocity in the nozzle 21 and acorresponding reduction in lift effect along the suction surface 13.

As shown in FIGURE 3, the control means 34 can, on the other hand, beeffective to increase the lift effect by moving the wall member 25 tothe full open position shown in FIGURE 3, wherein the maximum amount offluid is scooped into the passage 17 for discharge at increased velocitythrough the nozzle 21. As shown, the forwardmost or follower section 25ais, in this position, removed from the plane of the mouth 18 thusincreasing the size of the mouth 18 by an amount indicated by thereference indicia X so as to be coordinated with the increase in size ofthe passage 17. Thus, with this arrangement it can be seen an infinitelyvariable mass flow of fluid can be received, accelerated and directedthrough the restricted nozzle 21 for any desirable velocity flow fromthe egress orifice 19.

As best shown in FIGURES 3 and 4, the extensible joint 40 preferablytakes the form of a reduced tongue 41 integrally formed with the rearhalf of the section 25d, which tongue works in a slot 41a formed in theforward half of said section 25d. Sealing strips 42 of molded nylon orother suitable material may be provided along the entire length of theedges of the articulated wall member 25 for cooperation with theadjacent rib 15 (note FIGURE 4) so as to confine the stream of fluid tothe passage 17, as desired.

With reference once again to FIGURE 1 of the drawing, the deicing systemfor the leading edge 11 and the lift modifying passage 17 of the presentinvention will now be described. Thus, a blast nozzle 50 is positionedon the underneath side of the upper surface 13 and directed chordwisearound the interior of the airfoil 10 so as to direct a flow of heatedair in the direction shown by the flow arrows in this figure. The flowof air from the nozzle 50 may be regulated as desired by a suitablevalve 52 which serves to interconnect the nozzle 50 with a suitablesource of heated air 53, which for example, may be gained from theexhaust system of a piston engine, compressor bleed from a turbineengine, bleed from the aircrafts pneumatic system or any other suitablemeans carried by the aircraft. After the flow of heated air has passedover the entire surface of the wall member 25, it is received by adeflector horn 55 carried by the rear half of the section 25d and thendirected through a fixed transfer passageway 56 and out a dischargeorifice 57, which is located immediately upstream of the nozzle 21.

Similarly, the lower wall member 27 is provided with a suitable blastnozzle 60 for directing hot air along the same with a fixed transferpassageway 61 located adjacent a discharge orifice 62. These orifices57, 62 are provided with suitable flap valves 63, 64, respectively,which are pivoted on the upstream side of their respective orifices soas to operate in response to the differential in pressure between thehigh velocity fluid stream in passage 17 and the pressure of the heatedair exiting through the orifices 57, 62. These flaps valves 62, 64 allowthe proper proportioning of the mixing fluids for maximum efliciency andare effective to maintain the desired laminar flow of fluid through thenozzle 21. This is so since, as shown by the flow arrows in FIGURE 3,the flap valves 63, 64 form an interface between the streams at theorifices 57, 62 so that when they join in the nozzle 21 they are bothtraveling substantially parallel to the longitudinal axis of said nozzle21. It will be realized that the heated air entering the nozzle 21 notonly serves the important function of preventing and/or removing theformation of ice along said nozzle 21, but also serves to giveadditional mass flow and velocity to the lift modifying stream of fluidexiting through the egress opening 19.

As shown in FIGURE 2, when the articulated wall member 25 is positionedin the lower limit position, the flow of fluid into the mouth 18 and theaccelerating section 20 of the passage 17 will be cut off therebyallowing the flap valves 63, 64 to open to their full open position tocause the maximum flow of heated air through the nozzle 21. In this modeof operation the heated air will be effective to free the nozzle 21 ofice formations in the event that such should develop at any time duringoperation. After the nozzle 21 has been freed of ice in this position,the wall member 25 can be moved to the normal position of FIGURE 1whereby maximum flight efliciency can be resumed.

During any mode of operation it may be desirable to terminate the flowof heated air to the nozzles 50 by closing the valves 52 whereupon theflap valves 63, 64 will assume their fully closed position (note dottedline position of FIGURE 3) thus allowing the maximum flow of unheatedair from the pressure surface 14 to the suction surface 13.

In the modification of the deicing system shown in FIGURE 4, continuouspassageways 70-, 71 are formed from the blast nozzles 50, 60,respectively, to channel the heated air immediately adjacent therespective surfaces 25, 27. Thus, the passageway 70 is preferably formedby an articulated series of deflector members 75a.- 75d corresponding tothe articulated sections '25a25d with the sections being constrained formovement with the wall member 25 by provision of connecting links 76,which interconnect pivot pins 77 of the deflector member 75 with thecorresponding pivot pins 26 of the wall member 25. Similarly, the blastnozzle 60 is connected to the transfer passageway 61 by a continuousdeflector wall 78, as shown in this figure.

It should now be apparent to those skilled in this art that anadjustable lift modifying passage 17 has been provided with an efficientdeicing system wherein a maximum amount of deicing is obtained with aminimum amount of disturbance of the laminar flow of fluid in thepassage 17. Further, since the heated air is introduced directly intothe nozzle 21, the maximum amount of deicing etfect can be obtained inthis critical area. Also, of course, as pointed out above, theintroduction of the heated air into the nozzle tends to increase thevelocity and mass flow of the fluid thereby improving the overalloperation of the lift modifying passage 17.

In this disclosure, there is shown and described only the preferredembodiments of the invention, but, as aforementioned, it is to beunderstood that the invention is capable of various changes ormodifications within the scope of the inventive concept.

I claim:

1. In an airfoil having leading and trailing edges and relativelyfixedly spaced suction and pressure surfaces extending between saidedges, the improvement comprising a passage in said airfoil extendingsubstantially parallel to the fluid flow relative to said surfaces ofsaid airfoil, said passage being formed by opposed inner. wall membersin said airfoil, said wall members being spaced to form an enlargedmouth opening through said pressure surface and a restricted nozzleopening through said suction surface so as to form a high velocitystream of fluid and direct the same tangentially along said suctionsurface whereby to cause said fluid flow to follow said suction surface,at least one of said wall members being movable toward and away from theother wall member and means for selectively moving said one wall memberwhereby the cross sectional area of said passage may be adjusted to varythe mass flow of fluid through said passage and the velocity of saidstream exiting through said nozzle, said wall members being located atall times wholly between said relatively fixedly spaced surfaces, andone of said wall members being disposed for movement into and fromclosing relation with respect to said mouth opening.

2. The combination of claim 1 wherein said one wall member includesarticulated sections and an extensible joint whereby said mouth may beclosed by at least one of said sections when said one wall member ismoved to the limit position toward said other wall member.

3. The combination of claim 2 wherein the forwardmost one of saidsections is a follower section positionable in response to the movementof the second in-line section, said follower section being positionableacross a portion of said mouth to vary the size thereof in accordancewith the adjusted size of said passage.

4. In an airfoil having leading and trailing edges and relativelyfixedly spaced suction and pressure surfaces extending between saidedges, the improvement comprising a passage in said airfoil extendingsubstantially parallel to the fluid flow relative to said surfaces ofsaid airfoil, said passage being formed by opposed inner wall members insaid airfoil, said wall members being spaced to form an enlarged mouthopening through said pressure surface and a restricted nozzle openingthrough said suction surface so as to form a high velocity stream offluid and direct the same tangentially along said suction surfacewhereby to cause said fluid flow to follow said suction surface, atleast one of said Wall members being movable toward and away from theother wall member and means for selectively moving said one wall memberwhereby the cross sectional area of said passage may be adjusted to varythe mass flow of fluid through said passage and the velocity of saidstream exiting through said nozzle, said wall members being located atall times wholly between said relatively fixedly spaced surfaces, andone of said Wall members being disposed for movement into and closingrelation with respect to said mouth opening, means defining an orificeopening into said passage immediately upstream of said nozzle, meanscommunicating with said orifice for introducing heated air into saidnozzle to prevent the formation of ice, a flap valve for cooperatingwith said orifice to open and close the same, said valve being pivotedat its upstream edge so as to be responsive to the differential inpressure between said heated air and said high velocity stream.

5. The combination of claim 4 wherein said orifice communicates with theinterior of said airfoil and said means for introducing heated airincludes a blast nozzle positioned in said interior to direct heated airchordwise around the inside of said leading edge and back along said onewall member and deflector means for receiving said heated air anddirecting the same through said orifice.

6. In an airfoil having leading and trailing edges and relatively spacedsuction and pressure surfaces extending between said edges theimprovement comprising a passage in said airfoil extending substantiallyparallel to the fluid flow relative to said surfaces of said airfoil,said passage being formed by opposed inner wall members in said airfoil,said wall members being spaced to form an enlarged mouth opening at saidpressure surface and a restricted nozzle opening at said suction surfaceso as to form a high velocity stream of fluid and direct the sametangentially along said suction surface whereby to cause said fluid flowto follow said suction surface, deicing means for preventing theformation of ice along said Wall members including first and secondblast nozzle means on the interior of said airfoil for directing heatedair along the inside surfaces of said wall members, first and secondorifices formed in the respective wall members immediately upstream ofsaid nozzle for introducing said heated air into said nozzle wherebymaximum ice prevention is obtainable along the length of said passagewith flow of said heated air in said passage only through said nozzle.

7. The combination of claim 6 wherein are further provided first andsecond flap valves for cooperating with the respective orifices, saidvalves being pivoted at their upstream edge so as to be responsive tothe difiFerential in pressure between said heated air and said highvelocity stream, and means for adjusting the cross section of passageand said mouth to limit said stream and allow increased flow of heatedair through said nozzle.

8. The combination of claim 7 wherein said adjusting means includes atleast one of said wall members, said one wall member being formed ofarticulated sections, means for selectively moving said sections of saidone wall member toward and away from the other wall member, and anextensible joint in said one wall member, whereby said mouth may beclosed by at least one of said sections when said one wall member ismoved to the limit position toward said other member.

9. The combination of claim 7 wherein is further provided means forforming first and second continuous passageways along the inside of saidone and said other wall members, respectively, to confine the flow ofsaid heated air adjacent said wall members.

10. The combination of claim 8 wherein is further provided means forforming first and second continuous passageways along the inside of saidone and said other wall members, respectively, to confine the flow ofsaid heated air adjacent said wall members, said means for forming saidfirst passageway including a series of articulated deflectors connectedto said sections for adjustable parallel movement therewith.

References Cited UNITED STATES PATENTS 2,557,829 6/1951 Lavelle 244422,678,784 5/1954 Lanier 2444'2 3,326,500 6/1967 Lanier 244-42 MILTONBUCHLER, Primary Examiner. JAMES E. PITTENGER, Assistant Examiner.

